The present invention relates to a unique security control circuit for preventing the unauthorized use of a semiconductor memory incorporated within a microprocessor unit. Presently there is a need to protect programs and data stored in memory devices found in terminals and other data processing equipment from being read by unauthorized persons. With increasing emphasis directed towards software programs, the need to protect such programs also increases. Once a program or other data has been stored in a memory device associated with a widely-used microprocessor, it is very easy for one to remove the memory device and copy the program from the memory device using a similar microprocessor. Thus, it is the primary object of this invention to provide a circuit to prevent the unauthorized removal of information stored in a memory device. It is a further object of this invention to provide such a circuit which is simple in construction and low in cost.